1. Field of the Disclosure
The subject matter disclosed herein is generally directed to methods and apparatuses for monitoring and measuring fluid that is flowing through a conduit. More specifically, the present disclosure is directed to systems, methods, and apparatuses that may be used for obtaining samples of a fluid flowing through a conduit, and/or for determining the flow rate of the fluid flowing through the conduit.
2. Description of the Related Art
Drilling fluids are used when drilling or completing wells for a variety of reasons. Common uses for drilling fluids include: lubrication and cooling of drill bit cutting surfaces, cleaning the wellbore and transportation of cuttings to the surface, controlling formation pressure, maintaining well stability, and transmitting hydraulic horsepower to downhole motors.
Drilling fluids are pumped down through the drill string to the drill bit. The drilling fluids pass through the drill bit and then are returned back to the surface through the annulus between the outside of the drill pipe and the wellbore wall. To control formation pressure, maintain wellbore stability, lubricate the drill bit, and provide other functions, drilling fluids often include suspended additives, including barites, clay, and other materials. These additives are blended with the drilling fluid at the surface so that the drilling fluid being pumped through the drill string into the wellbore has the desired properties.
As the drilling mud exits the drill bit and returns to the surface, it may become mixed with drill cuttings and fluids from the formation. In order to maintain the composition of the drilling fluid being pumped into the drill string, the drilling fluid is cleaned and treated at the surface before being recirculated into the well. During the cleaning and treating process, the drilling fluid can be tested at a variety of locations and time intervals to determine fluid characteristics such as density and viscosity. In many applications, the testing of drilling fluid commonly requires the direct involvement of rig personnel, who oftentimes must manually obtain samples of the drilling fluid. These manually obtained drilling fluid samples are then analyzed using a variety of testing equipment and procedures known in the art.
Depending on the specific drilling rig setup and the overall configuration of the drilling fluid circulation system, manually obtaining drill fluid samples in an effective manner may be problematic. Moreover, as the overall automation of many common drilling rig operations continues to increase, it is recognized that automating the drilling fluid sample acquisition activity, that is, obtaining samples without the direct involvement of rig personnel, may also be advantageous.
One problem that must sometimes be addressed is the loss of circulation materials, i.e., drilling mud and its constituents, to the formation during the drilling operation. Depending on the characteristics of the geological formations being drilling through and the formulation of the drilling mud, a portion of the drilling mud may flow into one or more of the formations instead of returning up the annulus of the wellbore. In such cases, it can be difficult to adequately control pressures within wellbore since the hydrostatic load of the drilling fluid on the formation can be reduced below optimum levels. Furthermore, an increase of returned drilling fluid volume can sometimes occur, which may also be detrimental to the drill fluid characteristics. For example, the returned drilling fluid volume can increase due to the influx of liquids, gases, or both from the surrounding formation. In the event that the volume increase is due to additional liquid, then the mud weight can drop and the system used to control mud weight must make adjustments relatively quickly in order to maintain the proper pressure conditions within the well.
Accordingly, it is important to continuously monitor the flow rate of drilling fluid into the well versus the flow rate of the mixture of drilling fluid and drill cuttings, i.e., the drilling fluid mixture, back out of the well during the drilling operation so that the proper drilling environment, i.e., pressure and stability, is maintained within the wellbore. For example, when the flow rate of returned drilling fluid drops below the flow rate of drilling fluid into the well, the amount of drilling fluid pumped into the well can be increased in order to maintain the proper pressure gradient in the well. Additionally, in such cases the formulation of the drilling fluid can be adjusted to include so-called “lost circulation materials,” can reduce or even prevent the loss of drilling fluid into the surrounding formation by blocking and/or plugging porous areas in the walls of the wellbore. Accordingly, the ability to accurately monitor the flow rate of the returning drilling fluid in real time can often be an important aspect of an overall drilling operation.
In some prior art drilling applications, a “paddle wheel” type flow indicator is sometimes used to obtain an estimation of the flow rate of returned drilling fluid mixture through a flowline. In a paddle wheel type flow indicator, the paddle wheel—which typically consists of plurality of radial blades, or paddles, mounted on a rotating wheel—“floats” on the upper surface of the drilling fluid as the fluid flows through the flow line. In some cases, paddle wheel is mounted on a hinged support arm, which allows the paddle wheel to move up or down along an arc defined by the hinged support arm so that paddle wheel stays substantially on contact with the upper surface of the drilling fluid as the drilling fluid level changes within the flow line.
However, the prior art paddle wheel flow indicator has several limitations that are due at least in part to the fact that the paddle wheel, by design, only contacts the upper surface of the flowing drilling fluid. For example, since the paddle wheel normally floats along the upper surface of the drilling fluid as it flows through the flow line, it can only measure a surface velocity of the flowing drilling fluid, and not a true volumetric flow of the fluid. Furthermore, as drilling progresses during a typical drilling operation and drilling fluid and drill cuttings are returned from the wellbore, a bed of stationary drill cuttings may tend to build up, at least temporarily, in the bottom of the flow line, e.g., below the paddle wheel. Therefore, the accuracy of the paddle wheel flow indicator can be compromised as there is no way to accurately ascertain how much of the cross sectional area of the flow line has gradually become at least partially occluded by a bed of stationary drill cuttings that is sporadically present below the paddle wheel. Moreover, assuming that a substantially constant volumetric flow of returned drilling fluid is flowing through the flow line, the surface velocity of the drilling fluid—as measured by the paddle wheel—will gradually increase as the bed of stationary drill cuttings build up due to the partially occluded, i.e., reduced, flow area through which the returned drilling fluid flows.
This type of variation in the flow area of a flow can be further exacerbated during a common drilling operation known as a “sweep”. During the sweep operation, a relatively small amount of highly viscous fluid, or a relatively short term burst of a high volumetric fluid flow, is pumped down the well in order to “sweep” the well-bore clean of any drill cuttings that may have been too heavy to be carried up by the standard mud rheology. When this sweep of high viscosity or high flow rate fluid returns the surface, it is highly turbulent and carries a large amount of coarse particles. This fluid returning from the sweep operation also acts to rinse away the bed of stationary drill cuttings from the bottom of the flow line relatively quickly, thus causing a significant increase in the cross-section area that is available for flow. Accordingly, after the flow effects of the sweep operation have passed and normal operation resumes, there can often be a substantial decrease in the surface velocity of the flowing drilling fluid for any given value of volumetric flow, due at least in part to the temporary absence of the stationary bed of drill cuttings in the bottom of the flow line.
In view of the foregoing, there is a continuing need to accurately monitor and measure a flow of drilling fluid through a conduit during well drilling operations. The present disclosure is directed to various systems, methods, and apparatuses that may be used to address at least some of the issues and problems outlined above.